Photographic objective.



I 1 i I UNITED STATES Patented December 13, 1904.

PATENT OFFICE.

FRANZ URBAN, OF STEGLITZ, NEAR BERLIN, GERMANY, ASSIGNOR TO THE FIRM OFOPTISCHE ANSTALT C. P. GOERZ AKTIENGESELL- SOHAFT, OF FRIEDENAU, NEARBERLIN, GERMANY.

PHOTOGRAPHIC OBJ ECTIVE.

SPECIFICATION forming part of Letters Patent No. 777,320, dated December13, 1904.

Application filed June 9, 1904- To all whom it may concern.-

Be it known that I, FRANZ URBAN, Optician, a citizen of the GermanEmpire, residing at Steglitz, near Berlin, Germany, have invented a newand useful Improvement in and Relating to Photographic Objectives, ofwhich the following is a specification.

This invention relates to improvements in photographic objectives; andit consists more particularly in a spherically, astigmatically,chromatically, and comatically corrected fourlens objective.

In the new objective the spherical, astigmatical, and chromaticalcorrection is obtained in a substantially known manner by including alens of arbitrary character between two lenses of the oppositecharacter, forming with the first-mentioned lens one collective and onedispersive surface. In order to obtain at the same time comaticalcorrection, I divide one of the two outer lenses in said knowncombination into two lenses of the same character-that is to say, intotwo positive lenses when the original lens was positive and into twonegative lenses when the original lens was negative-choosing such kindsof glass for the two elements of the compound lens that the surfacebetween the element lenses has collective property and a curvatureopposite to that of the collective surface already present in the systemas above stated. The effect of the compound lens consisting of twolenses of the same character is substantially thesame as the effect ofone single lens of the same character, with the sole difference that thecollective surface between the lens elements of opposite curvature tothe other'collective surface of the system gives a means to counteractthe dispersive surface present in the system. This last-named surfaceisthe principal reason of the comatical fault of the system by itssubjecting the marginal rays of a pencil of inclined incidence todifferent degrees of deflection.

The four forms in which the objective modified according to the presentinvention can be constructed are illustrated in the an- Serial No.211,730. (No model.)

nexed drawings by means of central vertical sections.

Figures 1 and 2 represent the two forms of the objective in which one ofthe two outer positive lenses shown in Fig. 1 of the drawings annexed tothe Patent No. 528,155 is replaced by two positive lenses. In Figs. 1and 2 of the annexed drawings the central negative lens is indicated byb. In Fig. 1 a single positive lens a is shown on the right-hand side ofthe negative lens. as in Fig. l of the drawings annexed to the previouspatent cited; but the lens shown in the latter on the left-hand side isreplaced by two positive lenses (0' and a. In Fig. 2, on the other hand,a singlepositive lens a is placed on the left-hand side of the centralnegative lens; but two positive lenses 0 and 0 instead of a singlepositive lens are placed on the right-hand side of the central lens.

In the objective shown in Fig. 1 the cement surfaces between the lensesa (L2, on the one hand, and between the lenses 7) and c, on the otherhand, are collective, whereas the cement surface between the lenses aand Z; is dispersive.

In the objective shown in Fig. 2 the cement surface between the lenses 6and 0 and that between the lenses '0 and c are collective, and thecement surface between the lenses (1 and b is dispersive. In each casethe collective cement surfaces are of opposite curvature.

Figs. 3 and 4 illustrate those forms of the objective in which twonegative lenses are used in place of one of the outer negative .lensesshown in Fig. 2 of the drawings annexed to the previous patent cited. Inthe said Figs. 3 and 4 the central positive lens is represent by B. InFig. 3 the lateral negaand O respectively, and in Fig. 4 by A, A and C,respectively. In Fig. 3 the collective cement surfaces are between thelenses A and B and the lenses C and C the dispersive cement surfacebeing between the lenses B and O. In Fig. 4 the collective cementsurfaces are between the lenses A and A and tive members are representedby A and C the lenses A and B, the dispersive surface The improvedob'ectiv can be used either 5 as a smg e o ective or as a on e o ective.

I of a similar kind having a different focal 5 certained the nature ofmy said invention and 20 objectives built up of four lenses havingcebeing between the lenses B and C. In each of the said Figs. 3 and4=the collective cement surfaces are therefore of opposite curvature.

Coma elng correc e e ob ective 1s 1n form of a single objectiveparticularly well adapted to be used in a setthat is to say, incombination with an objective or objectives length or focal lengths forthe purpose of varying the focal lengths of the combination by combiningdifferent objectives of the set.

Having now particularly described and asin what manner the same is to beperformed, I declare that what I claim is The spherically,chromatically,astigmatically and comatically corrected photographicmented faces. and comprising a lens of arbitrary character, inclosedbetween lenses of the opposite character whereof one is double, forminga collective surface between its elements, and the other single, therefractive power of each of the individual lenses contacting withopposite sides of the first-mentioned lens being different from therefractive power of the lens with which it contacts and the contactingsurfaces being one dispersive and the other collective, the collectiveone having opposite curvature to the collective surface between theelements of the said double lens.

In testimony whereof I have signed this specification in the presence oftwo subscribing witnesses.

FRANZ URBAN.

Witnesses:

HENRY HASPER, WOLDEMAR HAUPT.

